I've been to many Brewer games over the years, having grown up in SE Wisconsin. Most of the fans that I've interacted with at Brewer-Cub games have been knowledgeable and friendly (except for a friend of mine that gets surly when the Cubs win). I suspect that represents the bulk of their fan base. There have been a handful of militant fans, but every fan base has jerks.
This is about the Brewer organization, though - not the fans. Several years ago, when a strike was looking like a possibility, I had seats a few rows behind home plate, so I created a sign that was critical (but not vulgar) of Don Fehr and Bud Selig. When I held it up between innings, it got a lot of attention - and an usher saw it and told me I could not display it - unless I removed the part critical of the Commissioner! Yes, censorship alive and well at Miller Park.
Now they've gone one better and fueled the inferiortiy complex perception. I've made several comments on here that I think the "anti-team" t-shirts that street vendors sell are lame - whether they are anti-Cub, Cardinal, Brewer, Packer, Bear, etc. Well, now the Brewers are selling a t-shirt in their official team store that says "Curse the Cubs" and has a goat on it. Personally, I find this hilarious on several levels.
It's amusing more than offensive, and if it's supposed to be offensive, it's that much more amusing.
As someone (Josh?) pointed out last year, the curse itself is a myth (and I don't give credence to the concept of a curse in the first place). Plus, Cub fans don't really buy into it, but fans of other teams insist that we do. It speaks volumes to me that they need to do this because they think that their fan base is likely to buy an anti-Cub shirt instead of a Brewer shirt . . . one can see anti-Cub shirts in Miller Park when the Cubs aren't even there, but I think that's a vocal minority. (That's not to say they the "mainstream" fans like the Cubs, but most can show a little more class than that.) You've got some pretty bush league marketing personnel working for you, Mr. Attanasio!